fal 0.9.0

fal allows you to run python scripts directly from your dbt project.

fal: do more with dbt

fal is the easiest way to run Python with your dbt project.

Introduction

With the fal CLI, you can:

• Send Slack notifications upon dbt model success or failure.
• Load data from external data sources before a model starts running.
• Download dbt models into a Python context with a familiar syntax: ref('my_dbt_model') using FalDbt
• Programatically access rich metadata about your dbt project.

Head to our documentation site for a deeper dive or play with in-depth examples to see how fal can help you get more done with dbt.

❗️ If you would like to write data back to your data-warehouse, we recommend using the dbt-fal adapter.

Getting Started

1. Install fal

$ pip install fal

2. Go to your dbt project directory

$ cd ~/src/my_dbt_project

3. Create a Python script: send_slack_message.py

import os
from slack_sdk import WebClient
from slack_sdk.errors import SlackApiError

CHANNEL_ID = os.getenv("SLACK_BOT_CHANNEL")
SLACK_TOKEN = os.getenv("SLACK_BOT_TOKEN")

client = WebClient(token=SLACK_TOKEN)
message_text = f"Model: {context.current_model.name}. Status: {context.current_model.status}."

try:
    response = client.chat_postMessage(
        channel=CHANNEL_ID,
        text=message_text
    )
except SlackApiError as e:
    assert e.response["error"]

4. Add a meta section in your schema.yml

models:
  - name: historical_ozone_levels
    description: Ozone levels
    config:
      materialized: table
    columns:
      - name: ozone_level
        description: Ozone level
      - name: ds
        description: Date
    meta:
      fal:
        scripts:
          - send_slack_message.py

5. Run fal flow run

$ fal flow run
# both your dbt models and fal scripts are run

6. Alternatively run dbt and fal consecutively

$ dbt run
# Your dbt models are run

$ fal run
# Your python scripts are run

Examples

To explore what is possible with fal, take a look at the in-depth examples below. We will be adding more examples here over time:

• Example 1: Send Slack notifications
• Example 2: Use dbt from a Jupyter Notebook
• Example 3: Read and parse dbt metadata
• Example 4: Metric forecasting
• Example 5: Sentiment analysis on support tickets
• Example 6: Anomaly Detection
• Example 7: Incorporate fal in CI/CD workflow
• Example 8: Send events to Datadog
• Example 9: Write dbt artifacts to GCS
• Example 10: Write dbt artifacts to AWS S3

Check out the examples directory for more

How it works?

fal is a command line tool that can read the state of your dbt project and help you run Python scripts after your dbt runs by leveraging the meta config.

models:
  - name: historical_ozone_levels
    ...
    meta:
      fal:
        post-hook:
          # scripts will run concurrently
          - send_slack_message.py
          - another_python_script.py

fal also provides useful helpers within the Python context to seamlessly interact with dbt models: ref("my_dbt_model_name") will pull a dbt model into your Python script as a pandas.DataFrame.

Running scripts before dbt runs

Run scripts before the model runs by using the pre-hook: configuration option.

Given the following schema.yml:

models:
  - name: boston
    description: Ozone levels
    config:
      materialized: table
    meta:
      owner: "@meder"
      fal:
        pre-hook:
          - fal_scripts/trigger_fivetran.py
        post-hook:
          - fal_scripts/slack.py

fal flow run will run fal_scripts/trigger_fivetran.py, then the boston dbt model, and finally fal_scripts/slack.py. If a model is selected with a selection flag (e.g. --select boston), the hooks associated to the model will always run with it.

$ fal flow run --select boston

Concepts

profile.yml and Credentials

fal integrates with dbt's profile.yml file to access and read data from the data warehouse. Once you setup credentials in your profile.yml file for your existing dbt workflows anytime you use ref or source to create a dataframe fal authenticates using the credentials specified in the profile.yml file.

meta Syntax

models:
  - name: historical_ozone_levels
    ...
    meta:
      owner: "@me"
      fal:
        post-hook:
          - send_slack_message.py
          - another_python_script.py

Use the fal and post-hook keys underneath the meta config to let fal CLI know where to look for the Python scripts. You can pass a list of scripts as shown above to run one or more scripts as a post-hook operation after a dbt run.

Variables and functions

Inside a Python script, you get access to some useful variables and functions

Variables

A context object with information relevant to the model through which the script was run. For the meta Syntax example, we would get the following:

context.current_model.name
#= historical_ozone_levels

context.current_model.meta
#= {'owner': '@me'}

context.current_model.meta.get("owner")
#= '@me'

context.current_model.status
# Could be one of
#= 'success'
#= 'error'
#= 'skipped'

context object also has access to test information related to the current model. If the previous dbt command was either test or build, the context.current_model.test property is populated with a list of tests:

context.current_model.tests
#= [CurrentTest(name='not_null', modelname='historical_ozone_levels, column='ds', status='Pass')]

ref and source functions

There are also available some familiar functions from dbt

# Refer to dbt models or sources by name and returns it as `pandas.DataFrame`
ref('model_name')
source('source_name', 'table_name')

# You can use it to get the running model data
ref(context.current_model.name)

write_to_model function

❗️ We recommend using the dbt-fal adapter for writing data back to your data-warehouse.

It is also possible to send data back to your data-warehouse. This makes it easy to get the data, process it and upload it back into dbt territory.

This function is available in fal Python models only, that is a Python script inside a fal_models directory and add a fal-models-paths to your dbt_project.yml

name: "jaffle_shop"
# ...
model-paths: ["models"]
# ...

vars:
  # Add this to your dbt_project.yml
  fal-models-paths: ["fal_models"]

Once added, it will automatically be run by fal without having to add any extra configurations in the schema.yml.

source_df = source('source_name', 'table_name')
ref_df = ref('a_model')

# Your code here
df = ...

# Upload a `pandas.DataFrame` back to the datawarehouse
write_to_model(df)

write_to_model also accepts an optional dtype argument, which lets you specify datatypes of columns. It works the same way as dtype argument for DataFrame.to_sql function.

from sqlalchemy.types import Integer
# Upload but specifically create the `value` column with type `integer`
# Can be useful if data has `None` values
write_to_model(df, dtype={'value': Integer()})

Importing fal as a Python package

You may be interested in accessing dbt models and sources easily from a Jupyter Notebook or another Python script. For that, just import the fal package and intantiate a FalDbt project:

from fal import FalDbt
faldbt = FalDbt(profiles_dir="~/.dbt", project_dir="../my_project")

faldbt.list_sources()
# [
#    DbtSource(name='results' ...),
#    DbtSource(name='ticket_data_sentiment_analysis' ...)
#    ...
# ]

faldbt.list_models()
# [
#    DbtModel(name='zendesk_ticket_data' ...),
#    DbtModel(name='agent_wait_time' ...)
#    ...
# ]


sentiments = faldbt.source('results', 'ticket_data_sentiment_analysis')
# pandas.DataFrame
tickets = faldbt.ref('stg_zendesk_ticket_data')
# pandas.DataFrame

Supported dbt versions

The latest fal version currently supports dbt 1.4.*.

If you need another version, open an issue and we will take a look!

Contributing / Development

We use Poetry for dependency management and easy development testing.

Use Poetry shell to trying your changes right away:

~ $ cd fal

~/fal $ poetry install

~/fal $ poetry shell
Spawning shell within [...]/fal-eFX98vrn-py3.8

~/fal fal-eFX98vrn-py3.8 $ cd ../dbt_project

~/dbt_project fal-eFX98vrn-py3.8 $ fal flow run
19:27:30  Found 5 models, 0 tests, 0 snapshots, 0 analyses, 165 macros, 0 operations, 0 seed files, 1 source, 0 exposures, 0 metrics
19:27:30 | Starting fal run for following models and scripts:
[...]

Running tests

Tests rely on a Postgres database to be present, this can be achieved with docker-compose:

~/fal $ docker-compose -f tests/docker-compose.yml up -d
Creating network "tests_default" with the default driver
Creating fal_db ... done

# Necessary for the import test
~/fal $ dbt run --profiles-dir tests/mock/mockProfile --project-dir tests/mock
Running with dbt=1.0.1
[...]
Completed successfully
Done. PASS=5 WARN=0 ERROR=0 SKIP=0 TOTAL=5

~/fal $ pytest -s

Why are we building this?

We think dbt is great because it empowers data people to get more done with the tools that they are already familiar with.

dbt's SQL only design is powerful, but if you ever want to get out of SQL-land and connect to external services or get into Python-land for any reason, you will have a hard time. We built fal to enable Python workloads (sending alerts to Slack, building predictive models, pushing data to non-data-warehouse destinations and more) right within dbt.

This library will form the basis of our attempt to more comprehensively enable data science workloads downstream of dbt. And because having reliable data pipelines is the most important ingredient in building predictive analytics, we are building a library that integrates well with dbt.

Have feedback or need help?

• Join us in fal on Discord
• Join the dbt Community and go into our #tools-fal channel